The present invention relates to bushings and more specifically a bushing for railroad equipment.
Bushings for railroad equipment have generally included brass. Other parts that have acted as bushings also include stainless steel. This is because of the severe environment in which railroad equipment operates, for example, extreme temperatures, from the very hot deserts to the very cold north. Bushings are generally used with a valve element generally connected to a piston responsive to differential pressure to open and close the valve. Seals, for example, O-rings and K-rings are provided on the valve element as it moves in the bushing. Lubricant between the bushing and the valve element may be affected by severe temperatures, as well as being diluted by water or solvents inherent in the railroad air system. Also, in certain environments, contaminants, for example, coal dust, score the brass bushing and affect its ability to seal with the O-rings or K-rings. Brass is not inexpensive and adds to the weight of the overall valve.
The present invention provides a bushing for a railroad control valve composed of aluminum having an anodized surface with a teflon layer at least where a valve element moves within the bushing. The teflon is preferably impregnated into the anodized surface or may be a continuous teflon sheet bound to the anodized surface. The anodized surface is a hard coat anodize having a thickness in the range of 0.0006 to 0.001 inches. The valve element includes at least one seal riding on the teflon surface without lubrication. The control valve is a pneumatic brake control valve and the valve element may be part of a piston of a vent valve, an emergency portion or service portion of the control valve.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.